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FORGET EACH ROOM!!!! You have a 3.5 ton system right now, it's working (moving air). Find out the TOTAL cfm the system is pushing RIGHT NOW and at what static pressure it's doing it at. THE TOTAL. If you are pushing 1000 at .8, you will never push 1400 at .05, .08 or .1

This will tell you if your duct system is large enough!

OK, now I'm starting to see the point of determining total cfm... in combination with ESP, not just to balance the system. I'd guess if it's only pushing 1000 cfm, for example, it's not operating at 3.5 ton capacity, maybe because the ductwork is inadequate? But if it's pushing 1400 now, one could assume it could push 200 cfm more?

But my basic question remains the same as before... How the h*** does one go about finding someone to evaluate ESP?

2nd question: You are in the best place to find that out. Use the search.

He who? If you mean me (Florida Joy), I'm a she.

If you mean search for a pro using this site's search, it shows zilch in my neck of the woods. Any other ideas where to search? What title does the specialist I'm looking for go by? Mechanical engineer? Building inspector? ????

Part of air balancing is determining total air flow. Along with that checking the static pressure. So you'll know how much air is moving, and if your duct work can support the required air flow for a 4 ton.

Part of air balancing is determining total air flow. Along with that checking the static pressure. So you'll know how much air is moving, and if your duct work can support the required air flow for a 4 ton.

OK, I see. Need some ideas on how to find someone qualified to determine air flow and static pressure. The contractor locator map link shows nothing for my area. What kind of company does this type of testing?

There are perfect solutions and near perfect solutions. At some point, unless you are NASA, the cost and benefit of going from near perfect to perfect simply don't match up.

It's fun watching the picture come into focus for folks. She (Joy) seems to be absorbing it pretty quickly.

-So, we know you are short airflow for 3.5 tons, but not how much.
-You'll be installing another return, which will definitely help but we don't know how much.
-We know your weatherization work has lowered the worst case load, likely to about 2.5 tons (still a high number for house size imo).
-It's unlikely you'll install less than a 3 ton replacement unit, 3 ton needs a LOT less airflow than 4 ton.
-If you install a 3 ton 2 stage, low stage will almost definitely have very efficient air flow.
-3 ton 2 stage will put you right smack where you need to be to efficiently carry your meat of the season load with little to no cycling losses.
-If you install communicating equipment it will tell you static at various stages.

So the question becomes, how much further you go to get comfortable that the 3 ton 2 stage is the right decision?

OK, this site lists one in my county, two in an adjacent county. However, they all do commercial/institutional work. They'd do mine, if I insisted, for a price... more than I'm willing to spend.

Still don't see the benefit of basicly doing an "engineering study" on a single story residence. I'm certain the existing ductwork will handle upsizing from 3.5 ton to 4 ton, my FPL energy survey tech said I'd have no problem doing so, as did EVERY SINGLE A/C contractor, even the one today, who I told I'd be willing to pay extra if the ductwork needed to be upgreded. I'm convinced I have good airflow on my 3.5 ton system (since it was repaired last week), and I'm satisfied that my ducts will handle the little extra flow from the 4 ton XL20i.

Don't see the need to add another 25 to 30% to my replacement cost... so enough about ESP and total cfm and air balancing already!

I'm sold on the XL20i 4ton communicating combo with the 950 t-stat. I had one final estimate this morning from another A/C company owner, so I'm now deciding among three contractors whose owners (not salesmen) are offering the same exact equipment, with the same rebates, for significantly different bottomline prices, depending on whether they'll do the electric under their in house EC license, have to hire an outside EC, or plan on getting away with doing their own unlicensed electric work (this worries me).

I opened another thread discussing the electric, so if you have comments on that issue, please use that thread.

Thanks for all your help! I will be posting pix of my old Rheem, which is running great since Wednesday. But I'll likely delay the replacement to see what my electric bill is with the repaired Rheem. Maybe until December, depending on when the Trane rebate ends.

It's fun watching the picture come into focus for folks. She (Joy) seems to be absorbing it pretty quickly.

-So, we know you are short airflow for 3.5 tons, but not how much.
-You'll be installing another return, which will definitely help but we don't know how much.
-We know your weatherization work has lowered the worst case load, likely to about 2.5 tons (still a high number for house size imo).
-It's unlikely you'll install less than a 3 ton replacement unit, 3 ton needs a LOT less airflow than 4 ton.
-If you install a 3 ton 2 stage, low stage will almost definitely have very efficient air flow.
-3 ton 2 stage will put you right smack where you need to be to efficiently carry your meat of the season load with little to no cycling losses.
-If you install communicating equipment it will tell you static at various stages.

So the question becomes, how much further you go to get comfortable that the 3 ton 2 stage is the right decision?

I was posting when you put this up, so I missed it before I posted my decision about not doing air balancing.

While I've decided on the 4 ton XL20i, that's not to say it's what the final solution will be. My contractors WILL DO MANUAL J, which is required by code, but only after I've commited to their company doing the work. If the results come out to 3 ton, we'll go with 3 ton. If it's 3.5 ton or more, we'll go with 4 ton.